Speed Converter

Written byOleh Soloninupdated 25 September 2026

Value

From

Result

Result62.137119

Road, sea, air and laboratory speeds

Convert km/h to mph for foreign speed limits, m/s for physics homework or knots for sailing and aviation. Exact factors, instant results.

Speed units split along professional lines: roads use km/h or mph, physics uses metres per second, ships and aircraft use knots. Crossing between them is a daily annoyance for drivers abroad and students alike.

Every factor here is exact. A knot is precisely one nautical mile per hour, which is 1.852 km/h — a definition tied to the size of the Earth rather than an arbitrary standard.

How to use

Enter a speed.
Choose the unit you are converting from: km/h, mph, m/s, knots or feet per second.
Choose the unit you are converting to. For km/h and m/s the calculator also shows the working.

Road speeds: km/h and mph

A mile per hour is exactly 1.609344 km/h. 100 km/h is 62.14 mph; 70 mph, the UK motorway limit, is 112.65 km/h.

Every row comes from the calculator on this page.
km/h	mph	mph	km/h
50	31.07	20	32.19
90	55.92	30	48.28
100	62.14	60	96.56
110	68.35	70	112.65
120	74.56
130	80.78

Knots, metres per second and the rest

Divide km/h by 3.6 for metres per second, multiply m/s by 3.6 for km/h. A knot is one nautical mile an hour, exactly 1.852 km/h.

Every row comes from the calculator on this page.
From	To
10 m/s	36 km/h
100 km/h	27.78 m/s
343 m/s, the speed of sound at 20 °C	1,234.8 km/h
1 knot	1.852 km/h
20 knots	37.04 km/h
500 knots	926 km/h
1 ft/s	1.097 km/h

What this calculator shows

The converted speed across five units, updating live
km/h and mph for driving, m/s for physics, knots and ft/s for specialist work
Enough precision to compare speed limits without rounding surprises

What to keep in mind

Uses exact definitions: 1 mph = 1.609344 km/h, 1 knot = 1.852 km/h.
These are scalar speeds; direction and wind correction are not part of the conversion.

FAQs

How fast is 100 km/h in mph?

62.14 mph. In the other direction 60 mph is 96.56 km/h and 70 mph is 112.65 km/h.

How do I convert km/h to m/s?

Divide by 3.6: 36 km/h is 10 m/s, 100 km/h is 27.78 m/s. Multiply by 3.6 to go back.

How many km/h is a knot?

Exactly 1.852 km/h, because a knot is one nautical mile per hour. 20 knots is 37.04 km/h.

Why do ships and planes use knots?

One knot is one nautical mile per hour, and a nautical mile is roughly one minute of latitude. So on a chart distance can be read straight off the latitude scale, and the distance run in nautical miles is simply speed in knots times hours: 10 knots for 2 hours is 20 nautical miles, or 37.04 km.

How do I convert m/s to km/h quickly?

Multiply by 3.6. Usain Bolt's top speed of about 12.4 m/s becomes roughly 44.6 km/h.

Is mph the same in the US and the UK?

Yes, both use the statute mile of 1.609344 km. It is the gallon, not the mile, where the two countries diverge.

Worked example

A German autobahn limit

Input: 130 km/h → mph

Output: 80.78 mph

Note: The advisory autobahn speed lands just above the 70 mph limit used across the UK.

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